Pressure fluid motor



May 23, 1939. E H sHAFF V2,159,232

PRESSURE FLUID MoToR Filed oct. 28, 195'?l QATTO Q91 Eye,

mama Mayas, 1939 :man PRESSURE FLUID nomi Ernest B. Shall, Grand Haven, lich., assigner toWlllismEKeller,lno.,Grandllaven,meh.,'

aoorporatianof man 0mm; as, im. sam Nn. 111,51

'I Claims.

'Ihe invention relates to motors adapted for actuation by pressure iiuid for driving such tools as portable screw drivers, and more particularly to motors of the type embodying an eccentric I relation in a cylinder of a rotor having generally radially movable vanes traversing the space between the rotor and cylinder to receive the driving force of the pressure fluid. A general object of the invention is to provide l0 a novel motor of this nature having improved features of construction enabling reversible operation with high eiliciency.

Another object is to provide a new and lmproved motor having high operating emciency which embodies an eccentric relation ofa rotor carrying generally radially movable vanes in a cylinder bore of elliptical cross section, as distinguished from a circular section, the rotor being located in close proximity to the bore wall sub- 20 stantially on the minor axis of the ellipse and the dimensions and shape of the ellipse being such as to produce an outward movementof the vanes to an effective position for substantially maximum power derivation during a minimum rotational 25 movement of the rotor.

Another object is to provide a new and improved reversible motor of thecharacter set forth including a novel arrangement of pressure iluid inlet and exhaust ports and a simple valve ar- 80 rangement controllingv the flow of motive uid.

In conjunction with the foregoing, another object stated more specifically is to provide, in a v motor having highly eilicient operating characteristics resulting from the coordination of a $5 vaned rotor and an elliptically shaped cylinder bore, an exhaust port which is constantly open to atmosphere and is common to a pair ofpressure fluid ports `capable of being connected selectively with a source of pressure uid by a simple revers- 40 ing valve mechanism to effect movement of the rotor in `one direction or the other.

Further objects reside in the provision of variousfeatures of construction and element relationships including means for positively extending the vanes into cylinder wall engagement by pressure fluid and a simplified arrangement o1' passageways for the flow of pressure fluid through the motor.

Other objects and advantages will become apparent in the following description and from the accompanying drawing, in which:

Figure 1 is a longitudinal axial section through a tool and motor embodying the features of the invention.

u l'igs.2and3aretransversesectionalviews taken substantially on the lines 2-2 and l-rl respectivelyof Pig. i and looking in the direction of arrows.

4 is a rear elevation of the tool shown in i inclll'lg. 5 is a view in perspective of the motor cyl- Fig. 6 is an expanded view showing the parts of the valve assembly in perspective.

While the invention is susceptible of various modiilcations and alternative constructions, I have shown in the drawing and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend u2 limit the invention to the specific form disclosed, but intend to cover all modifications 'and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

An important feature of the present invention is the relationship of parts by which a simple, yet highlyv eiiicient reversible pressure iluid actuated motor is obtained. As far as I am aware, it has heretofore been the practice in motors of this nature to mount a cylindrical vane carrying rotor eccentrically in a cylindrical bore.v High emciency in such a motor could only be obtained by subjecting the vanes to the force of pressure fluid throughout the major Jportion of a revolution, for example some two-thirds of a revolution, the exhaust of expended pressure fluid taking place through the remaining one-third of the movement.'` '1b make such a motor reversible necessitated the provision of separate exhaust ports controlled by separate valve mechanisms with the result that the motor was complicated and expensive.

According to the present invention, a cylindrical rotor is journaled for movement in a cylinder having a bore of generally elliptical cross section, the rotor being mounted eccentrically in the bore with on'e side of the rotor in close proximity to the wall of the bore. The point oi the smallest dimension of the space-between the rotor and the cylinder is preferably located approxi- I mately on the plane oi' the minor axis of the ellipse. 'Ihis point of smallest space dimension may, for convenience, be termed the point or line of running contact between the rotor and bore wall, although it is not essential that the rotor Il and the cylinder be actually in contact.

'111e dimensionsandshapeftheellipse,and with particular reference to the curvature of the borewalloneitherside ofthelineoi'runningcontact,ispreferablydeterminedbyabalaneebe tween two factors. For high emciency. it is desirable that the rotor varies be projected to their full working extent within the shortest possible distance of rotative movement of the rotor. Since in a reversible motor the fully projected vanes are forced inwardly of the rotor by the engagement thereof with the same portion of the bore wall which permits their outward movement, it is necessary that the slope of the bore wall be sufficiently gradual or slow to move the vanes inwardly of the rotor smoothly and without binding. A balance of these two coniditions will produce a motor having a high operating emciency.

In the present embodiment of the invention, the ellipse is shown as being in the form of a attened circle. Inthis form, the vanes will be projected substantially to their most emcient working position during approximately the iii-st third of a revolution, the position being determined approximately by the maior axis of the ellipse. This full projection of the vanes will, in a reversible motor, occur during the same distance of travel of a vane in either direction from the point of running contact. Through the distance 'between the points at which the vanes reach their fully extended position. at which points the dimension of the space between the rotor and cylinder is approximately at its greatest, the somewhat flattened circle form of ellipse provides a space which does not materially vary from that greatest dimension. The power derived by thevanes from the pressure fluid may, therefore, be almost completely transmitted to the rotor during approximately a half-revolution of the rotor. Without a loss of efficiency, therefore, an exhaust port which is permanently open to atmosphere, may be located at a point substantially diametrically opposed to the line of running contact. This exhaust port permits escape of expended pressure fluid from the space between the rotor and cylinder regardless of the direction of movement of the rotor and may, therefore, be said to' be common to both of the pressure uid inlets.

Merely for illustrative purposes. the present' invention has been shown as the prime moving element in a tool such as a portable screw driver. It is to be understood, however, that the invention may be readily used in other environments. Referring particularly to Fig. 1, the tool .structure' in its present embodiment comprises a sec-` tional casing including a rear section il. fashioned as a pistol grip for thel convenience of the operator, an intermediate cylindrical section Ii plate 2l may be secured in place by such\ an arrangement as annular spacing means 26 interposed between the'plate and a ring gear 29 fixed in the front casing section I2 for binding the front plate 2i against the cylinder end when the casing sections Il and I2 are secured together. The other end of the cylinder may be closed by a rear end plate 21 interposed between the end of the cylinder and the front face of the rear casing section -Il. Pins 28, or the like, extending between the front end plate 25 and the cylinder it, and from the cylinder through the rear end plate 21 into the rear casing section Il, may be employed to hold the parts against axial rotation or displacement.

'Ihe location of the rotor within the elliptical bore il is such that the axis of rotation of the rotor is located approximately on the plane of the shorter or minor axis of the bore, and is eccentricwith respect to the center of the bore to dispose one side of the rotor in close proximity to the bore wall. Preferably the rotor is substantially in running contact with the cylinder and the line of the smallest space dimension between the rotor and cylinder, is located approximately on the minor axis of the elliptical bore.

The rotor is provided with a series of radially extending peripherally opening slots 30 (Fig. 2) which are preferably equidistantly spaced in a circumferential direction. Each slot slidably supports a fiat member or vane 3l for radial projection into engagement with the opposed surface of the bore wall. In the present embodiment of the invention, it has been found that maximum efllciency of the motor is derived when six such vanes are used. During rotation, the varies will follow the contour` of the bore, an outward projection of the vanes being obtained as the result of centrifugal force acting thereon or by other means as will hereinafter be more particularly described. The driven movement of the rotor results from subjecting the portions of the vanes extending beyond the rotor to the force of a suitable pressure fluid, such as compressed air.

The wall of the cylinder along the so-called line of running contact is substantially thickened, as indicated at 32. Preferably, the pins 2l extend into the thickened portion of the cylinder substantially on the plane of said line. On each side of the plane of said line, the thickened portion of the cylinder has a longitudinally extending pressure fluid conducting passageway 3l. Il (see Figs. 2 and 5). Each passageway has a longitudinal sexies of ports l5, 3S respectively forming the matar housing, and. a front section\ opening the elliptical bore I8. "I'he and 36, therefore, open into the space between I2 within which driving gears I3 and a tool spindle Il are mounted. The casing sections are preferably detachably connected by screw threaded unions l5. I

The motor, which for the most part is housed within the casing section I I, comprises a cylinder I6 (Figs. 1 and 2) and rotor l1. The cylinder is elongated and has a bore Il therein which is of elliptical cross section. The rotor is an elongated cylinder xed as by a key I! to a shaft 2l dimensioned to extend through and beyond each end of the rotor and cylinder. Its rear end is carried by a bearing 2l seated in a suitable recess 22 formed in the front end face of the rear casing section l0. The other end" of the shaft is journaled in a similar bearing 23 mounted within a circular flange 24 preferably formed as an integral part of an end plate 25 which abuts and closes the front end of the cylinder I6. The end the cylinder and the rotor on opposite sides of the narrowest space dimension therebetween.

An exhaust for pressure fluid from the space between the rotor and the cylinder is, in the present instance, provided by means of a lport 31 or series of ports located substantially in diametrically opposed relation to the line of running contact between the rotor and cylinder. The exhaust is permanently open to atmosphere and preferably the ports 31 open into an annular space 38 provided by appropriately recessing the inner wall of the casing section Il. An annular series of ports 39, through the casing section Il and communicating with the recess 38, permits escape of pressure fluid from the casing. If desired, an annular ring Il seated upon the casing section il in overlying relation to the ports Il Il maybeprovidedasabameforpressureiiuidissuingfromtheportslltobreaktheforceofthe escaping pressure fluid and reduce the noise.

Pressure huid for operating the motor is supplied tothepresentdevicethrougha passage formed in the-handle portion of the rear section Il. a normally closed valve l! isinterposed between the passage Il and a continuation passage u, the valve 'being adapted for manipulation by such means as a finger piece u. The passage leads forwardly of the casing section il to a simple reversing valve mechanism. generally indicated at il, locatedat the front end of the rearv section in convenient position for ready manipulation by the operator.

The reversing valve mechanism Il is best seen in Figs. 1, 4 and 6. Thusthe casing sectionil is transversely bored to receive a cylindrical member Il constituting a valve seat. The cylin- Q drical memberis suitably secured rigidly to the rear section and has a port 41 in open communication with 'the passage 'Ihe valve seat has a pair of ports 4l and 4l, each in open communication with an upwardly rising bore l (see Fig. 1) in the rear section il. lhe bores Il communicate with apertures Il and l2 in the rear end plate 21, which apertures in turn communicate respectively with passageways Il and Il in the cylinder.

A cylindrical valve Il is arranged to ilt snugly and rotatably in the valve seat I and may be suitably held therein by such means as interengaging screw and washer arrangements Il, Il. at each end of the valve and valve seat. 'Ihe washer in the securing arrangement Il may conveniently be utilized to eii'ect manipulation of the valve. To this end, a projection I8 is struck out of the washer for engagement with a recess ll formed in the associated end face of the valve 53. -A manipulable finger piece il, extending from the washer, preferablyhas a shank portion engageable in an arcuate recess Il cut in the end of the valve seat and serving to limit rotational movement of the valve.

The valve 53, opposite to the port l1 in the valve seat, has an annular groove Il. Extending longitudinally of the valve from the groove are recesses 0I, 62 appropriately positioned to establish selective connection between the groove 80 and the ports I8. I0 respectively. It will be evident that by this valve arrangement, it is only necessary to move the valve into one oi' two positions in order to eilect a delivery of pressure fluid to the space between the rotor and the cyl inder on one side or the other of the line of rimnlng contact, thus effecting a driven movement of the rotor in one direction or the other. Since the exhaust ports I1 are permanently open to atmosphere, it is unnecessary in the present device to provide valve means for controlling the escape oi' pressure uid from the motor.

As each vane moves past exhaust, a relatively small quantity of air will be trapped in the space between the rotor and the cylinder. It is, therefore. desirable to provide means for exhausting air from these spaces. With reference to Fig. 5, the external surface of the cylinder immediately beyond the passages 33 and ll is longitudinally cut away, as at 63. M. In assembly, these cutaway portions or recesses 83. 8l are open to atmosphere through the annular space 3l and ports 39 in the casing section I l. 'I'he rear end plate 21 has apertures 65, i6 (Figs. 2 and 3) communieating respectively with the recesses Il, I4 and bores (not shown) in the rear casing section Il similartothepreviousiydescrlbedboresllead from the apertures 0I, respectively to ports l1, 0I (ll'ig. 6) in the valve seat 4l. The valve has recesses Il and `Il disposed substantially in longitudinal aiinement with the recesses 62 and Il, respectively. The recess 0I. is dimensioned and arranged to establish communication between the pressure'iluid inlet port 4l and the adjacent port C1 when the recess I2 is positioned to direct a flow of pressure fluid into the inlet passage 33 of the cylinder, and the recess`1l is similarly arranged to establish communication between the ports Il and il 'when the recess Il connects the inlet passage Il with a source of pressure fluid. Hence, whenever the valve is set to direct a now of pressure iluid into one or the other of the passages Il. Il, the other .pas-

sage 34 or is at the same time connected with atmosphere.

In operation, and 'presuming that the valve ll is set to direct a ilow of pressure fluid into the passage u, the rotor will be driven clockwise (Fig. 2). Due to the elliptical shape of the cylinder bore, the vanes will be extended to substantially their fullest eective working position within a relatively short rotational distance so that substantially the 'entire available energy of the pressure iiuid will be transmitted to the rotor during the movement oi' each vane through a half-revolution. At the end of a half-revolution, the expended pressure fluid exhausts from the space behind each vane through the permanently open ports I1, which, being common to each of the intake passages u. Il, permits the motor to be readily reversed through the soie agency of a single simple valve mechanism.

desired, means may be provided to supple-y ment the action of centrifugal force in moving the blades outwardly whereby positively to insure complete proiection of the blades during motor operation. 'Ib this end, the rear end plate 21 has a pair. of substantially diametrically opposite arcuate grooves 1i, 12 formed in the rotor abutting face thereof as shown in Fig. 3. The grooves are positioned to communicate with the inner portions of the vane receiving slots and are dimensioned to extend from approximately the point occupied by a vane when pressure fluid is ilrst admitted to the space behind the vane to a point which stops just short of the position occupied by a vane when it reaches the exhaust port Il. Passages 13,1 lead from the grooves 1|, 12 respectively to the pressure fluid intake ports Il, 52. The front end plate I5 may have similar grooves 1I, I2 therein, but since the iront plate 25 is not provided with intake ports Il, 52, corresponding recesses are formed therein to register with and receive pressure fluid from the front ends of the pressure uid passages I3, I4. It will be evident that when pressurel iluid is delivered to either one of the passages 33, 3l, for example the passage Il, a small volume of pressure fluid willbe by-passed through the passage 14 to the groove 12 and thence into the slots behind the vanes. The opposite intake passage 33, being at the same time connected with atmosphere, the pressure fluid behind each vane will exhaust through the opposite groove 1I and passage 'Il to permit ready retraction of the vane into the rotor.

In the present embodiment the driving gears il are preferably arranged as a series of planetary gears for driving the tool spindle Il. Thus, the front end of the shaft 20 is fixed to a center pinion or sun gear Il arranged to mesh with a 'plurality of planet gears 1G which, in turn, en-

From the foregoing, it will be evident that bya novel and simple construction a reversible pressure fluid actuated motor has been provided which has a high operating eillciency.

I claim as my invention:

1. A reversible pressure fluid operated motor comprising, in combination, a cylinder having a bore oi' elliptical cross section, a rotor journaled for rotation eccentrically in said bore in close proximity to the bore wall substantially on the minor axis of the ellipse, said rotor having six equidistantly spaced substantially radial slots therein, a vane slidably seated in each slot for projection into wiping engagement with the bore wall during rotor movement, said ellipse being dimensioned to permit movement oi said vanes outwardly substantially to their fully projected position in less than one-half of a complete revolution of said rotor, said cylinder having a permanently open exhaust port to atmosphere located approximately in diametrically opposed relation to the point of close proximity of the rotor and bore wall, and having an inlet passage on each side of said point leading to the space between the rotor and bore wall, a source of pressure fluid, and a single reversible valve adapted selectively to connect either of said inlet passages with said source'and the other inlet passage with atmosphere.

l 2. A reversible pressure fluid operated motor comprising,l in combination, a cylinder having a bore of elliptical cross section, a rotor eccentrically journaled in said bore on an axis located substantially on the plane of the minor axis of the ellipse, said rotor having a plurality of spaced slots therein, vanes slidably seated in said slots for movement into engagement with the bore wall during rotor movement, the shape of said ellipse being such as to permit movement of said vanes outwardly substantially to their fully projected position in about one-third of a complete revolution of said rotor, said cylinder having an inlet passage leading to each side of the narrowest space between the rotor and bore wall, said cylinder having a permanently open exhaust port to atmosphere located approximately in diametrically opposed relation to said inlet passages, a source of pressure fluid, and a reversible valve adapted selectively to connect either of said inlet passages with said source.

3. A reversible pressure fluid operated motor Y comprising, in combination, a cyllnderhaving a narrowest spacing between the rotor and bore wall, and a source of pressure fluid adapted to be connected with said inlet passage.

4. In a device of the character described, the combination of a cylinder having a -bore of oval cross section as distinguished from one of circular cross section, a rotor Journaled for substantially running contact with a wall of the bore only along a line located approximately on the plane of a narrower cross dimension of the bore, varies mounted in said rotor for movement relative thereto in a substantially radial direction into engagement with the bore wall, and means providing pressure fluid passages communicating with the space between said rotor and bore wall at a point substantially opposite to the line of running contact and at a point closely adjacent to said line.

5. A pressure fluid motor having, ln combination, a cylinder provided with a bore, a rotor journaled for rotation in said bore with an eccentric relationship providing a line of close proximity between the rotor and bore wall, a plurality of substantially radially projectable members carried by said rotor for engagement with the bore wall during rotor movement, said bore wall being shaped to slope arcuately away from said rotor beyond said line to reach substantially its maximum spaced distance from the rotor surface at a point approximately 120 removed from said line, means for introducing pressure fluid between said wall and rotor adjacent to said line, and means providing an exhaust for fluid pressure located approximately 180 from said line of close proximity.

6. In a pressure fluid motor, the combination of a cylinder having a bore of elliptical cross section, a rotor mounted for rotation about an axis eccentric of the bore center and located substantially on the plane of the minor axis of said bore, a plurality of radially movable members carried by said rotor for engagement with the bore wall, the elliptical form of the bore being such that the space between the rotor and the bore wall increases on either side of the narrowest space dimension therebetween to reach substantially the greatest space dimension approximately at the ends of the major axis of the ellipse, said space intermediate the increasing portions having generally the same greatest space dimension therebetween, means for introducing pressure fluid into said space on either side of its narrowest dimension, and an open exhaust from said space diametrically opposite said narrowest dimension.

7. A pressure fluid motor having, in combination, a cylinder provided with a bore of elliptical cross section, a cylindrical rotary member having a plurality of radially movable vanes mounted therein, means for rotatably mounting said member in said bore with said member located in close proximity to the bore wall substantially on the shorter axis thereof, and means for operatively introducing and exhausting pressure fluid to and from the space between said member and bore wall, the pressure fluid exhausting means being located substantially diametrically opposite to the line of close proximity.

ERNEST H. SHAFF. 

